There are several reports from other laboratories that glyoxylate accumulates during thiamine (vitamin B1) deficiency. The present project is directed toward establishing whether elevated levels of glyoxylate, a known toxin, can account for the specific symptoms of thiamine-related disorders. The levels of two-carbon intermediates and the metabolic effects of these intermediates are being investigated. The metabolism of tissues affected by thiamine deficiency is being compared with that of tissues not affected in order to determine if there is a metabolic basis for the differential tissue susceptibility to thiamine deficiency.